Osteoid osteoma

Osteoid osteoma
Diagnosis in short
Osteoid osteoma. H&E stain.
LM	anastomosing bony trabeculae with variable mineralization, osteoblast rimming, no nuclear atypia of osteocytes
LM DDx	osteoblastoma, osteosarcoma
Site	bone (femur > tibia > spine > elsewhere)
Clinical history	pain relieved by NSAIDs
Symptoms	extremely painful
Radiology	<= 1.5 cm (larger lesion osteoblastoma)
Clin. DDx	osteosarcoma

Osteoid osteoma, abbreviated OO, is benign primary bone tumour. It is grouped with the chondro-osseous tumours.

General

• Benign bone lesion.

Clinical:

• Extremely painful.
  • Relieved by NSAIDs.

Gross

• Bone: femur > tibia > spine > elsewhere.
• Most common location (in bone): diaphysis.
• Must be less than 2 cm - as per WHO definition. ‡
  • Larger lesions with the same microscopy are osteoblastomas.

Note:

• ‡ Previously, the diagnostic size cutoff was <=1.5 cm.

Images:

• Osteoid osteoma - gross (umdnj.edu).
• Osteoid osteoma (uthscsa.edu).

Microscopic

Features:

• Anastomosing bony trabeculae with:
  • Variable mineralization.
    • Mineralization (calcium phosphate) = purple on H&E stain.
  • Osteoblast rimming.
    • Cells line-up at edge of bone.

Note:

• Histomorphologically near identical/indistinguishable from osteoblastoma; one needs some history to make the diagnosis.

Images

• 

  Osteoid osteoma - low mag. (WC)

• 

  Osteoid osteoma - intermed. mag. (WC)

• 

  Osteoid osteoma - high mag. (WC)

• 

  Osteoid osteoma - very high mag. (WC)

www:

• Osteoid osteoma - CT scan (med.utah.edu).
• Osteoid osteoma (sciencephoto.com).

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BONE, RIGHT FEMUR, EXCISION:
- OSTEOID OSTEOMA.

Micro

The sections show anastomosing bony trabeculae with variable mineralization and osteoblastic rimming. Multinucleated osteoclasts are scattered through the lesion. Hemosiderin-laden macrophages are present. No osteocyte nuclear atypia is apparent. Mitotic activity is not apparent. The osteoid is not lace-like.

See also

• Chondro-osseous tumours.
• Bone.